thenewkid

So my lt1 has some issues I can't seem to figure out... When I'm driving (usually when I'm just giving it a little gas) it will miss or sputter and when I let off the gas it sometimes backfires. I can definitely feel some power loss along with poor mpg. On the scanmaster, I've noticed a difference between the left and right pulses. No codes at this time. It has new spark plugs, wires, optispark, 02's, fuel pump, fuel injectors, fuel filter. not sure where to go next I would appreciate any help.

Injuneer

What year is your car?

Is the engine stock, slightly modified or heavilly modified? If modified, what has been done?

Did you have the problem BEFORE you changed all the parts you listed, or did it develop AFTER you replaced those parts?

When you indicate "On the scanmaster, I've noticed a difference between the left and right pulses." do you mean the left and right injector pulse widths? If so, how large is the difference? Under what operat9ing condition do you see these differences - idle, cruising, WOT? Does the difference correlate to differences in the left and right BLM's? Pulse widths are affected by the block learn multipliers.

thenewkid

94 Camaro, The engine only has bolt ons. I've replaced these parts in an attempt to fix my problem. I feel like the car started doing this after the head gasket blew a few years back. And yes by pulse I mean pulse widths, I just gathered these numbers after the engine reached operating temp at Idle: SP:20-25, LP:2.3, RP:1.8, LBL & RBL:160, LIN:162, RIN:128 let me know if you need anymore

Injuneer

While the Scanmaster is a convenient device for real time monitoring (I've had mine for about 18 years), it isn't as good for diagnostics as a data log run with good scanning software. The 160 BLM's indicate it's running lean, and the PCM is adding at least 25% extra fuel to prevent it from running lean. The 160 INT on the left indicates even adding 25% extra fuel with the left BLM, it's still running lean, so the PCM has jacked up the short term fuel correction (INT) to add even more fuel. Since the BLM and INT are multipliers in the fuel equation, it's adding 56% extra fuel on the left. But only 25% on the right, hence the left pulse width is longer than the right pulse width.

I would strongly recommend running a data log with Scan9495. But before that check the fuel pressure.

The data log allows us to look at every sensor and PCM parameter at the same time. While you could continue to page through the readings on Scanmaster, to add things like MAF flow, fuel correction cell #, O2 sensor millivolts, etc., there is a time lapse between each reading. The PCM is updating about 9 times per second.

thenewkid

Good info I will try to check the fuel pressure tomorrow, although I don't know anything about running a data log or scan9495. Could you point me in the right direction?

Injuneer

https://www.camaroz28.com/forums/com...95-lt1-874306/

thenewkid

The fuel pressure is fine... Ill let you know about the data log as soon as I get my hands on a laptop

Injuneer

What is "fine"? Did you test it out on the road, under load?

thenewkid

43.5 psi at idle with the vacuum line disconnected and blocked

Injuneer

If you have the correct fuel pressure at idle, and the BLM's you posted above (160 both sides) are for the idle cell (#16), you could have an MAF sensor giving low readings, or a large amount of air bypassing the MAF sensor.

Check the rubber elbow for tears, or the bottom not being fully on the throttle body. Make sure the plastic silencer tube hasn't come loose from the elbow. Make sure the MAF sensor is facing in the correct direction. Check for large vacuum leaks - brake booster line, EVAP line at throttle body, PCV air supply line at throttle body. Make sure the screws that hold the throttle body to the manifold are tight, and the gasket is intact.

At idle, are the O2 sensor readings cycling rapidly between 0XX and 9XX millivolts?